Tag Archives: Iron Age

“The way I see it, if you want the rainbow, you gotta put up with the rain.”

Anyone new to this blog or geophysics in archaeology is recommended to read the material on the “Geophysical survey in archaeology” page.

As I start this entry of the blog, the rain is splashing against my windows as was predicted by the Met Office. Although we might question Dolly Parton’s grammar, the sentiment seems true enough.  Yesterday, however, was a superb day with all three techniques collecting data across the site.

After yesterday’s excellent results, the GPR crew had great expectations.  The only problem was a tree in the way under which the shepherdess had put hay when the grass in the field was dead from lack of rain.  Unfortunately, sheep mean sheep droppings (Figures 1 and 2).

Figure 1: Mike on sheep poo removal duty.

Figure 2: Check out those wheels!

Luckily for everyone concerned, I think the effort was worth it (see Figure 3)!

Figure 3: GPR time slices from Day 18.

I could misquote Dolly along the lines of putting-up with sheep poo if you want excellent GPR results but I might be pushing my luck…  The many buildings are quite obvious in this data set.

Figure 4 shows this grid in context of the other GPR grids in this area.

Figure 4: GPR results including the day 18 data (SW corner).

We have added a very large number of new buildings to the map of Verulamium.  As I was only just starting with GPR data when we started collecting it in 2015, the processing keeps changing a bit from block to block. One of my jobs is to start from scratch and reprocess the whole thing so that the maps are consistent.  Should keep me busy for a while.  Figure 5 is a crude mosaic of images just showing the entire area surveyed so far.

Figure 5: crude mosaic of GPR time slices at the end of the 2018 season.

This represents 19ha of GPR data collected at 0.5m transect intervals.  Just pushing the machine along the lines, not including getting to the block, setting-up, moving strings etc. is 380km.  It also means 380km of radargrams!  No wonder the data takes-up 33gb of my hard disk and consists of over 70,000 files.

The mag team completed nine 40x40m grid squares which is 1.44 hectares.  Excellent progress!

Figure 6: the mag team in the southern field.

Figure 7 shows the whole of the 2018 survey (along with a big chunk of Verulamium).

Figure 7: the mag survey after day 18.

Even though we have been using the machine for some years now, and it does have its frustrations, when all is going well we can really cover some ground.  The season was planned for 20 days: we lost 3 days to rain, and most of a day to testing the mag at the start.  Despite this, the team have managed to collect 17.7 hectares of mag data.  Without actually getting to the grids and back (which is quite a bit of walking in itself), the team have pushed the cart 88.5km over the past four weeks.

Figure 8 shows the southern area in more detail.

Figure 8: the southern area of mag data after day 18.

The blue arrows in Figure 8 indicate the lines of old field boundaries.  These can be seen on old maps such as the 1699 parish map.  The yellow arrows mark ferrous objects.  Some are very big, but there are a scatter of smaller ones too.  Last, but definitely not least, there are a few magnetic features which may be archaeological, such as pits.  I have picked a few out with red arrows.  Although they look small at this scale, they are probably 1m to 2m across, a quite respectable size for a pit.

Although large mainly  blank areas are disappointing to collect, they are important nonetheless. The immediate environs of Verulamium are extremely rich, archaeologically. The field lies:

  • 360m W of the busy area of buildings recorded by the GPR discussed above;
  • 600m NE of the major Iron Age settlement at Prae Wood;
  • 600m N of the fields at Windridge Farm where metal detecting rallies have taken place;
  • 500m NW of the major cemetery at King Harry Lane;
  • 1,100m SE of Gorhambury Roman villa;
  • 1,000m NE of the new villa found at Windridge Farm.

Also, the Fosse, which is preserved in the woodland along the NE edge of the field, is a really very impressive earthwork.   We just seem to have hit an empty bit of landscape between all these sites!

The res survey now covers some 6.58ha, that is about 263,200 earth resistance readings.  Not into the millions like the mag and GPR, but this is res after all!  Figure 9 shows the entire survey.

Figure 10: the entire Earth Resistance survey after day 18.

At this scale the roads show very nicely as do some of the more substantial buildings.  Figure 11 is the area surveyed in 2018.

Figure 11: Res survey after day 18.

Given that the fields were baked hard and the grass was dead at the start of the season, I am pleased we managed any Earth Resistance survey at all this season.  The team yesterday put-up with my geophysics OCD and completed right into the corner by the theatre. We then doubled-back and started filling-in between the top of the survey block and the drive.  We have picked-up some parts of buildings seen in grids to the south, but in general along the edge the deep colluvium, as shown by the sunken nature of the drive, is to some extent masking the archaeology.

Many thanks to everyone on the team who made the 2018 season such a success.  A especially big thanks to those who helped move the equipment about including Ellen, Mike, Jim and Ruth.

For those who haven’t been involved but would like to join future surveys, do get in touch.  We are a friendly group, and provide on-the-job training.

And finally… (as they used to say on the news)

 

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Another day, another town

You would think I would have had enough. But no… hot on the heels of the end of the Gorhambury season, we headed off to the mysterious east side of the county. The Greenwich meridian seems to exert a powerful influence in Hertfordshire with its citizens seemingly afraid to cross the invisible line.

Back at the start of the project, we planned to do some survey in and around Braughing.  We managed just one site. The area is extremely important with multiple late Iron Age and Roman sites including the Roman “small town” on Wickham Hill.  We had an opportunity to work on the small town along with members of the Braughing Archaeological Group for a couple of days, mainly to see if magnetometry would show something useful.  The field was, however, rather rough and caused the odometer on the cart to over-run by about a meter, and the nuts and bolts needed constant tightening. On the second day I adjusted the odometer settings which improved matters a bit.

The survey underway on Wickham Hi

The survey underway on Wickham Hill.

We managed to complete 13 grid squares which was pretty good going, especially as the data logger crashed three lines before the end of the fourteenth square and we lost the rest of the grid.  The results, after a bit of work in TerraSurveyor, were very interesting.

The survey results.

The survey results.

The broad line running east-west towards the south of the surveyed area is the road.  It can be seen in the Google Earth image in the background.  Towards the west, the very dark band must be where the road becomes a sunken way as it goes up the slope.  What is very obvious is the difference to the planned public town at Verulamium.  This site was clearly a very different type of settlement.  What we have clearly shown is that it is worth expanding the magnetometry survey to cover as much of the settlement as possible.  Hopefully, the field surface will be a little more benign when we return!  One thing won’t change, however, and that is the slope…

On top of the hill.

On top of the hill.

Many thanks to Jim West for coming all the way from Chorley Wood to run the mag on the first day while I lay-in the grid, and also many thanks to all the members of BAG who joined in. Looks like we’ll be back!

A grey day in Ashwell

The weather forecast wasn’t great, but we took a chance and headed up to Great Buttway, Ashwell End, to continue our survey before the grass starts growing and we have to take a break until after the first silage cut.  Great Buttway was surveyed ten years ago using a single sensor machine by Mark Noel.  The survey was excellent, showing all sorts of Iron Age and Roman features.  The only reason for re-doing it is that we are now able to survey at a higher data density allowing us to create sharper, clearer pictures..

A grey day surveying in Ashwell.

A grey day surveying in Ashwell.

Luckily for us, the rain held off and we managed to survey the equivalent of about 11 grid squares: eight whole ones and four partials.  An excellent day’s work.  Many thanks to Dave Minty, Nigel Harper-Scott and Jim West who joined Ellen and I today.

The dGPS I have been using has had its SIM card changed to another service provider.  What a difference that made, and laying in the grid was a breeze.  Amazing technology, really, and revolutionizes how easy it is to georeference surveys.

The survey in Great Buttway after day 6.

The survey in Great Buttway after day 6.

The survey has linked up the Roman settlement in the NW corner of the area with the Iron Age settlement in the middle of the plot.  A road, presumably Roman, runs NW–SE across the area past the inevitable modern services.

The Roman site at Great Buttway / Wayman's field.

The Roman site at Great Buttway / Wayman’s field.

The detailed view of the Roman site shows more enclosures either side of the proposed road.  We can even see post-hole buildings in the eastern enclosure.  A very pleasing result.

We are hoping to go back to the site next week.  Hopefully, it’ll be a little warmer!  Also look out for further postings about Verulamium and a survey in the Candover valley.

Little Hadham

Today we ventured out to the east of the county to survey near Little Hadham. We had done a little survey at the site last autumn but returned to examine a more fruitful looking field today.  Many thanks to all who turned out, we had quite a large team.  As we wanted to finish the area we knew contained features we worked on until 6pm.  I think the results were worth the effort.

Results of the survey on 6th April 2014.

Results of the survey on 6th April 2014.

The surface finds included late Iron Age and Roman pottery and it looks like we have a small enclosed farmstead with an associated field system.  Clearly the features go further to the south and east, and metal detector finds show that it continues to the west on the other side of the road.  Previous survey suggests there is not much more, if anything, to the north.

The ridges from the cultivation show in the plot as the lines to running east-west, and there is a little stagger error, but nothing too bad.  We can’t always survey on nice smooth parkland!

Another success for the CAGG team!

Muddy day at Watton

Last Friday, Jim West, Ellen and I spent a cold and muddy morning trying to complete the survey at Broomhall Farm, Watton-at-Stone.  This survey has a long history.  It started as a training exercise for UCL students in 2008 when we surveyed a small area of a piece of pasture using a variety of instruments.  We found two ditches, one of which proved to be Roman and one from the cusp of the Iron Age/Roman periods.  Two years later I had to teach another geophysics course and so we returned.  More interesting features were revealed and so the Welwyn Archaeological Society surveyed the majority of the pasture with the Bartington.  In addition to the original two ditches we found two sides of a possible enclosure and a horseshoe shaped feature in the middle.  Again, they all were very late Iron Age / early Roman.  (Many thanks to Isobel Thompson for looking at the ceramics for WAS.)  The finds included a Dressel 1b amphora handle.

Fast-forward to May 2013 and we had our training day with the Foerster cart system in the pasture, and the first “real site” we surveyed was in the arable field called Cartway to the east of the original pasture.  Unfortunately we ran out of time due to the crops and so we have now returned with the aim of completing the survey of this exciting site.

Unfortunately, the mud hindered the operation of the cart!

The muddy wheels.

The muddy wheels.

We did, however, manage to complete four partial squares before the weather and the mud finally drove us away,

The magnetometer surveys at Six Acres/Cartway.

The magnetometer surveys at Six Acres/Cartway.

The image of the results is a rather crude mash-up of the Bartington and Foerster surveys as I have to convert our floating grid coordinates into real-world coordinates before I can plot them accurately,  The survey to the west inside the field boundaries is the Bartington, that to the east the Foerster,  In the Foerster data it appears that we have picked up a series of ditches which are probably field and enclosure ditches surrounding a small Roman period farmstead.  It is probable that the western enclosure had gone out of use in the early Roman period but the Roman farmstead continued to be occupied.

I will be adding some more pages to this blog with descriptions of some of the sites we are working on, and of the techniques we have been using.

We could do with some more help finishing these sites.  I realise that working in the mud and cold is not as attractive as in the sunshine in Verulamium Park!

Change of plans

Due to the terrible weather forecast for tomorrow (Friday), we decided to change our plans and try and squeeze a few grids in this afternoon at our new site at Ashwell.  Many thanks to Jim West for foregoing his sail boarding and coming out to help at short notice this afternoon.  Despite the wind, it was mostly a nice afternoon although we did have one heavy shower in the middle of the first grid.  We managed six grids in three hours, a respectable tally.  We have a further ten grids surveyed in ready for Saturday.

A large proportion of the field has previously been surveyed by Mark Noel, a commercial geophysicist with Geoquest, in 2003–6.  We are surveying the bits that weren’t covered in those previous surveys, as the Iron Age settlement in particular clearly spreads further to the south and east.

The plot (see below) is pleasingly good with many clear features and some very subtle ones.  The image has been cropped to +/- 2.5nT, i.e., much more than Verulamium where most of the images are cropped to +/-9nT.  The main problem with surveying here is that the odometer is less accurate than on the mowed lawns of the Park.  We are getting about a 0.8-1m over-run which I am having to “destagger” in TerraSurveyor.  Tomorrow I’ll adjust the odometer settings to try and eliminate that problem on the weekend.

The first day's results from the site near Ashwell.

The first day’s results from the site near Ashwell.

Hope to see some of you on Saturday and Sunday.  Contact the usual address for instructions.

Adventures in Braughing

Firstly, the mystery of the “big pipe” at Verulamium has been solved,  It is a 12″ gas main.  I assume it is buried quite deeply, but has a massive magnetic signature which swamps the signal.

Last weekend saw us looking at the first of our sites at Braughing.  The area is well known for its Roman “small town” and its Iron Age remains although the pattern is quite complex.  The site appears to be “multifocal”, a posh way of saying there is stuff spread about all over the place.  The first site we examined at the suggestion of Mark Landon was in a smallish pasture which had recently been cut for hay.

Clare Lewis and I met with Mark on Saturday to lay in the grid.  We had put in two base points with the dGPS earlier in the year.  Unfortunately, we couldn’t find the second point, which was necessary as a backsight for the total station.  After over an hour of pulling up stinging nettles and troweling back the surface we gave up and I just guessed the backsight with the intention of laying out the grid which we could tie into the OS National Grid later.  The next day, ably assisted by members of the Braughing Archaeological Group, we looked again for the backsight point with no luck,  Just as we had finished for the day and were about to go home the point was finally found.  Ellen and I quickly surveyed in the grid pegs to get the actual OS grid references.  Much to our amazement we found that the pegs were between 5 and 25cm out.  “Good enough for government work”, as they say…

We had quite a team out on the Sunday,  Ruth Halliwell (WAS) and Keith Bradbury (CVAS) were helped by members of the Braughing Archaeological Group / East Herts Archaeological Society including Mark Landon, Caroline Baigent, Bridget Edgson, Richard Maddams, Carolyn Westlake and Anne Rowe.  As a result we managed nine grids and completed the entire field in a day.

The site lies under a meter of alluvium and so it was going to be a challenge to detect anything much.  There is clearly a site there, Mark pulled a piece of samian, an imbrex and a piece of coin mould out from the bank of the river,  The normal processing (see figure below) didn’t show too much.

The first site at Braughing, normal data processing.

The first site at Braughing, normal data processing.

There is one circular high magnetic feature which is probably an oven, as well as some rather mysterious linear features running across the site.  Jarrod Burks suggested a route for a more high contrast plot.
Higher contrast processing, with Mark's annotation.

Higher contrast processing, with Mark’s annotation.

I’m not sure I can see anything much else in the plot, although with the eye of faith — or is it optimism? — Mark wonders if the features he has marked with red dots might be a building. We have been spoiled at Six Acres and Verulamium with such clear results.  This sort of “ink blob” result is more usual!  Any guesses as to the linear features?  They look more like geology than archaeology to me, but any suggestions welcome.

This week sees us back in Verulamium Park.  The weekend is going to be busy with the Magna Carta celebrations in the Park.  We are not certain if we are going to be there Saturday or Sunday as yet, we will check the weather forecast later in the week.

As the harvest approaches we will be wanting to get onto our rural sites.  We are still in urgent need of people to take charge of the organisation of some of these including contacting landowners.  Can you help?